When applying a picture texture to an object it comes out as kind of cut in half diagonally and distorted, is there a fix for this?
Blender doesn't know how to apply the image to the object, so it does all that stuff because it doesn't know what else to do. You need to tell it how to apply the image by making a UV map. The default cube in Blender comes with it's own UV map so you can follow these steps:

1) With the default cube selected open up the UV tab in the top bar



You should see a layout like this:


2) Export the UV map


Make sure you have this box checked and export


3) The UV map will be exported as a PNG. Edit it in whatever photo editing, drawing program you want to use. (eg. Photoshop, Illustrator, Firealpaca) 
In your case you would take your tree image and place it in the same spot that I put my blob.


4) Export your edited UV map and go back into Blender. Click the Shader Editor tab in the top bar and you should come up with a window that looks like this:


5) Copy the node setup shown below. In the image texture node press open and select your UV map that you put your picture on.


If everything is done right you should end up with something like this: 


Hope this helps! IDK if I explained this very well. If you have any questions pls ask. Blender has a steep learning curve but once you do learn it it's great. :D